Neurofilament light chain and tau concentrations are markedly increased in the serum of patients with sporadic Creutzfeldt-Jakob disease, and tau correlates with rate of disease progression

OBJECTIVES: A blood-based biomarker of neuronal damage in sporadic Creutzfeldt-Jakob disease (sCJD) will be extremely valuable for both clinical practice and research aiming to develop effective therapies. METHODS: We used an ultrasensitive immunoassay to measure two candidate biomarkers, tau and neurofilament light (NfL), in serum from patients with sCJD and healthy controls. We tested longitudinal sample sets from six patients to investigate changes over time, and examined correlations with rate of disease progression and associations with known phenotype modifiers. RESULTS: Serum concentrations of both tau and NfL were increased in patients with sCJD. NfL distinguished patients from controls with 100% sensitivity and 100% specificity. Tau did so with 91% sensitivity and 83% specificity. Both tau and NfL appeared to increase over time in individual patients, particularly in those with several samples tested late in their disease. Tau, but not NfL, was positively correlated with rate of disease progression, and was particularly increased in patients homozygous for methionine at codon 129 ofPRNP. CONCLUSIONS: These findings independently replicate other recent studies using similar methods and offer novel insights. They show clear promise for these blood-based biomarkers in prion disease. Future work should aim to fully establish their potential roles for monitoring disease progression and response to therapies

Amyloid-β nanotubes are associated with prion protein-dependent synaptotoxicity

Growing evidence suggests water-soluble, non-fibrillar forms of amyloid-β protein (Aβ) have important roles in Alzheimer's disease with toxicities mimicked by synthetic Aβ1-42. However, no defined toxic structures acting via specific receptors have been identified and roles of proposed receptors, such as prion protein (PrP), remain controversial. Here we quantify binding to PrP of Aβ1-42 after different durations of aggregation. We show PrP-binding and PrP-dependent inhibition of long-term potentiation (LTP) correlate with the presence of protofibrils. Globular oligomers bind less avidly to PrP and do not inhibit LTP, whereas fibrils inhibit LTP in a PrP-independent manner. That only certain transient Aβ assemblies cause PrP-dependent toxicity explains conflicting reports regarding the involvement of PrP in Aβ-induced impairments. We show that these protofibrils contain a defined nanotubular structure with a previously unidentified triple helical conformation. Blocking the formation of Aβ nanotubes or their interaction with PrP might have a role in treatment of Alzheimer's disease

Identification of a Compound That Disrupts Binding of Amyloid-β to the Prion Protein Using a Novel Fluorescence-based Assay

The prion protein (PrP) has been implicated both in prion diseases such as Creutzfeldt-Jakob disease, where its monomeric cellular isoform (PrP(C)) is recruited into pathogenic self-propagating polymers of misfolded protein, and in Alzheimer disease, where PrP(C) may act as a receptor for synaptotoxic oligomeric forms of amyloid-β (Aβ). There has been considerable interest in identification of compounds that bind to PrP(C), stabilizing its native fold and thereby acting as pharmacological chaperones to block prion propagation and pathogenesis. However, compounds binding PrP(C) could also inhibit the binding of toxic Aβ species and may have a role in treating Alzheimer disease, a highly prevalent dementia for which there are currently no disease-modifying treatments. However, the absence of a unitary, readily measurable, physiological function of PrP makes screening for ligands challenging, and the highly heterogeneous nature of Aβ oligomer preparations makes conventional competition binding assays difficult to interpret. We have therefore developed a high-throughput screen that utilizes site-specifically fluorescently labeled protein to identify compounds that bind to PrP and inhibit both Aβ binding and prion propagation. Following a screen of 1,200 approved drugs, we identified Chicago Sky Blue 6B as the first small molecule PrP ligand capable of inhibiting Aβ binding, demonstrating the feasibility of development of drugs to block this interaction. The interaction of Chicago Sky Blue 6B was characterized by isothermal titration calorimetry, and its ability to inhibit Aβ binding and reduce prion levels was established in cell-based assays

Repetitive Immunization Enhances the Susceptibility of Mice to Peripherally Administered Prions

The susceptibility of humans and animals to prion infections is determined by the virulence of the infectious agent, by genetic modifiers, and by hitherto unknown host and environmental risk factors. While little is known about the latter two, the activation state of the immune system was surmised to influence prion susceptibility. Here we administered prions to mice that were repeatedly immunized by two initial injections of CpG oligodeoxynucleotides followed by repeated injections of bovine serum albumin/alum. Immunization greatly reduced the required dosage of peripherally administered prion inoculum necessary to induce scrapie in 50% of mice. No difference in susceptibility was observed following intracerebral prion challenge. Due to its profound impact onto scrapie susceptibility, the host immune status may determine disease penetrance after low-dose prion exposure, including those that may give rise to iatrogenic and variant Creutzfeldt-Jakob disease

Peripheral Administration of a Humanized Anti-PrP Antibody Blocks Alzheimer's Disease Aβ Synaptotoxicity.

Alzheimer's disease (AD) is associated with pathological assembly states of amyloid-β protein (Aβ). Aβ-related synaptotoxicity can be blocked by anti-prion protein (PrP) antibodies, potentially allowing therapeutic targeting of this aspect of AD neuropathogenesis. Here, we show that intravascular administration of a high-affinity humanized anti-PrP antibody to rats can prevent the plasticity-disrupting effects induced by exposure to soluble AD brain extract. These results provide an in vivo proof of principle for such a therapeutic strategy

UK Iatrogenic Creutzfeldt-Jakob disease:Investigating human prion transmission across genotypic barriers using human tissue-based and molecular approaches

Creutzfeldt-Jakob disease (CJD) is the prototypic human prion disease that occurs most commonly in sporadic and genetic forms, but it is also transmissible and can be acquired through medical procedures, resulting in iatrogenic CJD (iCJD). The largest numbers of iCJD cases that have occurred worldwide have resulted from contaminated cadaveric pituitary-derived human growth hormone (hGH) and its use to treat primary and secondary growth hormone deficiency. We report a comprehensive, tissue-based and molecular genetic analysis of the largest series of UK hGH-iCJD cases reported to date, including in vitro kinetic molecular modelling of genotypic factors influencing prion transmission. The results show the interplay of prion strain and host genotype in governing the molecular, pathological and temporal characteristics of the UK hGH-iCJD epidemic and provide insights into the adaptive mechanisms involved when prions cross genotypic barriers. We conclude that all of the available evidence is consistent with the hypothesis that the UK hGH-iCJD epidemic resulted from transmission of the V2 human prion strain, which is associated with the second most common form of sporadic CJD

Interaction between prion protein and toxic amyloid beta assemblies can be therapeutically targeted at multiple sites

A role for PrP in the toxic effect of oligomeric forms of A beta, implicated in Alzheimer's disease (AD), has been suggested but remains controversial. Here we show that PrP is required for the plasticity-impairing effects of ex vivo material from human AD brain and that standardized A beta-derived diffusible ligand (ADDL) preparations disrupt hippocampal synaptic plasticity in a PrP-dependent manner. We screened a panel of anti-PrP antibodies for their ability to disrupt the ADDL-PrP interaction. Antibodies directed to the principal PrP/A beta-binding site and to PrP helix-1, were able to block A beta binding to PrP suggesting that the toxic A beta species are of relatively high molecular mass and/or may bind multiple PrP molecules. Two representative and extensively characterized monoclonal antibodies directed to these regions, ICSM-35 and ICSM-18, were shown to block the A beta-mediated disruption of synaptic plasticity validating these antibodies as candidate therapeutics for AD either individually or in combination

Infestation of Transgenic Powdery Mildew-Resistant Wheat by Naturally Occurring Insect Herbivores under Different Environmental Conditions

A concern associated with the growing of genetically modified (GM) crops is that they could adversely affect non-target organisms. We assessed the impact of several transgenic powdery mildew-resistant spring wheat lines on insect herbivores. The GM lines carried either the Pm3b gene from hexaploid wheat, which confers race-specific resistance to powdery mildew, or the less specific anti-fungal barley seed chitinase and β-1,3-glucanase. In addition to the non-transformed control lines, several conventional spring wheat varieties and barley and triticale were included for comparison. During two consecutive growing seasons, powdery mildew infection and the abundance of and damage by naturally occurring herbivores were estimated under semi-field conditions in a convertible glasshouse and in the field. Mildew was reduced on the Pm3b-transgenic lines but not on the chitinase/glucanase-expressing lines. Abundance of aphids was negatively correlated with powdery mildew in the convertible glasshouse, with Pm3b wheat plants hosting significantly more aphids than their mildew-susceptible controls. In contrast, aphid densities did not differ between GM plants and their non-transformed controls in the field, probably because of low mildew and aphid pressure at this location. Likewise, the GM wheat lines did not affect the abundance of or damage by the herbivores Oulema melanopus (L.) and Chlorops pumilionis Bjerk. Although a previous study has revealed that some of the GM wheat lines show pleiotropic effects under field conditions, their effect on herbivorous insects appears to be low

Characterization of inflorescence-predominant chitinase gene in Metroxylon sagu via differential display

Chitinase is an enzyme that catalyzes the degradation of chitin, commonly induced upon the attack of pathogens and other stresses. A cDNA (MsChi1) was isolated from Metroxylon sagu and expressed predominantly in the inflorescence tissue of M. sagu, suggesting its role in developmental processes. The chitinase cDNA was detected and isolated via differential display and rapid amplification of cDNA ends (RACE). Primers specific to M. saguchitinase were used as probes to amplify the 3′-end and 5′-end regions of chitinase cDNA. Transcript analysis showed that chitinase is expressed in inflorescence and meristem tissues but was not detected in the leaf tissue. Sequence analysis of amplified cDNA fragments of 3′-end and 5′-end regions indicated that the chitinase cDNA was successfully amplified. The M. saguchitinase cDNA isolated was approximately 1,143 bp long and corresponds to 312 predicted amino acids. Alignments of nucleotide and amino acid have grouped this chitinase to family 19 class I chitinase

Potential human transmission of amyloid β pathology: surveillance and risks

Studies in experimental animals show transmissibility of amyloidogenic proteins associated with prion diseases, Alzheimer's disease, Parkinson's disease, and other neurodegenerative diseases. Although these data raise potential concerns for public health, convincing evidence for human iatrogenic transmission only exists for prions and amyloid β after systemic injections of contaminated growth hormone extracts or dura mater grafts derived from cadavers. Even though these procedures are now obsolete, some reports raise the possibility of iatrogenic transmission of amyloid β through putatively contaminated neurosurgical equipment. Iatrogenic transmission of amyloid β might lead to amyloid deposition in the brain parenchyma and blood vessel walls, potentially resulting in cerebral amyloid angiopathy after several decades. Cerebral amyloid angiopathy can cause life-threatening brain haemorrhages; yet, there is no proof that the transmission of amyloid β can also lead to Alzheimer's dementia. Large, long-term epidemiological studies and sensitive, cost-efficient tools to detect amyloid are needed to better understand any potential routes of amyloid β transmission and to clarify whether other similar proteopathic seeds, such as tau or α-synuclein, can also be transferred iatrogenically